Rotating coalescers are utilized in crankcase ventilation (CV) systems for removing oil from crankcase blow-by gases. Typically, the blow-by gases enter the rotating coalescer device axially at the center of the device. The gases are turned 90 degrees, pass through a rotating coalescer section, and exit radially from the outer face of the rotating coalescer device. The rotating coalescer device itself is in the form of a ring and the space in the middle of the ring is either left open or optionally includes radial vanes which facilitate flow through the device.
Rotating coalescers may include fibrous filters as well as centrifugal separation devices. Performance attributes of rotating coalescer devices may be measured in terms of pressure drop (or rise) through the device and efficiency of oil removal. In rotating coalescers, the oil droplets (e.g., aerosol) suspended and transported by the blow-by gas are separated inside the coalescer media through the particle capture mechanisms of inertial impaction, interception, and diffusion. By rotating the media, inertial impaction is enhanced by the additional centrifugal force. In addition to this aspect, after the oil droplets coalesce to form larger drops, the centrifugal force removes the larger drops by overcoming the surface drag force of the media fibers. This aspect increases the coalescence of the oil from the coalescer by providing improved drainage compared to a stationary coalescer. In turn, the improved drainage from the rotating coalescing filter aids in improving the filtration efficiency as well as greatly reducing the pressure drop across the filter.